Flame tube



M. LAND FLAME TUBE May 28, 1968 Filed Oct. 12, 1966 United States Patent3,385,054 FLAME TUBE Martin Land, Derby, England, assignor toRolls-Royce Limited, Derby, England, a British company Filed Oct. 12,1966, Ser. No. 586,298 Claims priority, application Great Britain, Oct.20, 1965, 44,503/65 3 Claims. (Cl. 60-39.65)

ABSTRACT OF THE DISCLOSURE The disclosure of this invention pertains toa flame tube for a gas turbine engine combustion chamber in which a heatretaining hollow member is positioned in the upstream end of the flametube so that primary combustion takes place within said member and theinner surface of said member is isolated from all cooling air wherebysaid member becomes very hot and this fact will in itself promotecombustion.

This invention concerns a flame tube, e.g. for a gas turbine enginecombustion chamber.

According to the present invention, there is provided a flame tube forgas turbine engine combustion equipment having an inlet at its upstreamend through which a fuel/air mixture may be supplied to the flame tube,the inlet having a maximum diameter which is substantially less than themaximum diameter of the flame tube, a one-piece part-spherical memberformed of a ceramic material which is mounted at the upstream end of theflame tube and within which, in operation, primary combustion occurs,the upstream end of the said member communicating with the said inletbut being otherwise completely unapertured, the downstream end of thesaid member having a diameter which is substantially the same as thesaid maximum diameter of the flame tube, and means through which a flowof cooling air may be supplied to the internal surface of the flametube, completely by-passing the interior of the said member so that thelatter remains completely uncooled in operation.

Combustion is promoted in the flame tube of the present invention byreason of the fact that the said partspherical member becomes very hotsince cooling air does not flow over its internal surface.

The said member is preferably formed of densely sintered siliconnitride. Thus the specific gravity of the sintered silicon nitride ispreferably at least 3.0.

The flame tube is preferably substantially cylindrical, although thepresent invention is also applicable to an annular flame tube.

The flame tube preferably has a plurality of axially consecutivesections with annular gaps therebetween, the annular gaps being suchthat cooling air supplied thereto will flow over the internal surfacesof the respective sections.

The said member may be mounted within the upstream one of said sectionsand may be connected thereto by at least one expansion joint.

The invention also comprises a combustion chamber for a gas turbineengine in which there is mounted at least one flame tube as set forthabove.

Additionally, the invention comprises a gas turbine engine having such acombustion chamber.

The invention is illustrated, merely by way of example, in theaccompanying drawings, in which:

FIGURE 1 is a diagrammatic view, partly in section, of a gas turbineengine having a combustion chamber provided with flame tubes inaccordance with the present invention, and

FIGURE 2 is a broken-away sectional view on a larger scale of part ofone of the flame tubes of FIGURE 1.

In FIGURE 1 there is shown a gas turbine jet propulsion engine 10 havingan engine casing 11 in which there are mounted in flow series acompressor 12, a combustion chamber 13, and a turbine 14, the turbineexhaust gases being directed to atmosphere through an exhaust duct 15.

Mounted in the combustion chamber 13 are a plurality of angularly spacedapart substantially cylindrical flame tubes 16.

Each of the flame tubes 16 has a plurality of axially consecutivesections 20, an annular gap 21 being provided between the downstream endof each section 20 and the upstream end of the adjacent section 20.Mounted in each of the annular gaps 21 is a corrugated annular member 22which serves to space the adjacent sections 20 from each other.

Air which has been compressed by the compressor 12 is supplied to theexterior of the flame tubes 16 and enters the annular gaps 21 so as toflow over the internal surfaces of the sections 20. This is indicated bythe arrows 23.

The most upstream of the sections 20 has a reduced diameter portion 24at its upstream end which forms an inlet through which a fuel/ airmixture may be supplied to the flame tube. As will be seen from FIGURE2, the diameter of the inlet 24 is substantially less than the maximumdiameter of the sections 20.

Mounted in the inlet 24 is a swirl device 25 for effecting mixing of airfrom the compressor 12 with fuel which is delivered thereto from a fuelmanifold 26.

Mounted within the said upstream section 20 is a onepiece member 30which is part-spherical in shape. The member 30 has a sliding connectionwith expansion joints 31 which are mounted in the upstream section 20.Apart, however, from the apertures to receive the expansion joints 31,and apart from its open upstream and downstream ends, the member 30 isun-apertured.

The member 30 is made of ceramic material such as densely sinteredsilicon nitride (e.g. of specific gravity 3.1 to 3.2), its constructionbeing such that it will withstand the heat from the primary combustionwhich in operation occurs within it.

If desired, the member 30 may have its downstream end extending to thedownstream end of the upstream section 20.

The upstream end of the member 30 communicates with the inlet 24 and hasa diameter which is substantially the same as the diameter of the inlet24. The downstream end of the member 30, however, has a diameter whichis substantially the same as the maximum diameter of the flame tube 16.

The upstream section 20 has apertures 32, through which a supply ofcooling air may flow to the internal surface of the upstream section 20.

As will be noted, however, the construction of the flame tube is suchthat no cooling air will flow over the internal surface of the member30. The member 30 is therefore maintained very hot from the primarycombustion occurring within it, and this will, in itself, promotecombustion.

I claim:

1. A flame tube for gas turbine engine combustion equipment having aninlet at its upstream end through which a fuel/ air mixture may besupplied to the flame tube, the inlet having a maximum diameter which issubstantially less than the maximum diameter of the flame tube, aone-piece part-spherical member formed of a ceramic material which ismounted at the upstream end of the flame tube and within which, inoperation, primary combustion occurs, the upstream end of the saidmember communicating with the said inlet but being otherwise completelyunapertured, the downstream end of the said member having a diameterwhich is substantially the same as the said maximum diameter of theflame tube,

and means through which a flow of cooling air may be supplied to theinternal surface of the flame tube, completely by-passing the interiorof the said member so that the entire inner surface of said member iscompletely isolated in operation from any cooling air.

2. A flame tube as claimed in claim 1 in which the flame tube comprisesa plurality of axially consecutive sections which define annular gapstherebetween, the said member being mounted within the upstream one ofsaid sections, there being provided at least one expansion joint toconnect the said member to the upstream one of said sections.

3. A flame tube as claimed in claim 1 wherein said ceramic material issilicon nitride.

References Cited UNITED STATES PATENTS 2,602,292 7/1952 Buckland et a16039.74 2,686,655 8/1954 Schorner 60-39.65 XR 2,956,399 10/1960 Beighley60-39.71 XR 2,958,194 11/1960 Bayley 6039.65

JULIUS E. WEST, Primary Examiner.

